This proposal is to continue studies designed to elucidate the multiple factors which control myocardial perfusion and function. Although the work will not be carried out in human subjects, each of the proposed studies is designed to answer questions of importance in defining the physiology or pathophysiology of cardiac function in man during health and disease. To this end, whenever possible, studies are carried out in awake animals; animal models simulating human cardiovascular disease are employed. The research proposal contains six general categories: 1. Response of coronary vasculature to brief perturbations. 2. Interaction between myocardial blood flow and mechanical properties of the left ventricle. 3. The role of purine metabolism in determining myocardial function following brief ischemia. 4. Collateral development and function in dogs and pigs. 5. Myocardial blood flow in the hypertrophied ventricle. 6. Myocardial mechanics in the hypertrophied ventricle.